1. Field of the Invention
The present invention is generally related to a pushbutton switch with a means provided to prevent actuation of the switch following a relamping procedure and, more specifically, a pushbutton switch that comprises a plunger and a base which are both provided with discontinuities in their shape which are moved into interference relation with each other in response to the plunger being pulled away from the base by a predetermined distance followed by the plunger being pushed toward the base.
2. Description of the Prior Art
In many applications of pushbutton switches, it is necessary to provide a provision which permits the button to be pulled away from the switch body to permit the lamps within the pushbutton to be changed. After the lamps are changed, it is necessary to return the pushbutton actuator to its normal position by pushing the button inward toward the switch body. However, in certain applications it is important that the switch not be actuated during this procedure. Those skilled in the art are familiar with several techniques used to accomplish this function.
U.S. Pat. No. 4,254,315, which issued to Stevens on Mar. 3, 1981, discloses a back-lighted push-button switch with a safety stop. The panel mounted pushbutton assembly has an illuminated button which is removable from the front of the panel. The device is provided with a safety locking mechanism for preventing accidental operation of the pushbutton switch when the pushbutton is reinserted into an operative position. The locking mechanism includes a cam member having a groove engaged by a cam follower. The groove is in the form of a closed loop path. The pushbutton is linked to the locking mechanism so that movement of the pushbutton moves the cam follower relative to the cam member along the groove. In the normal operating position, the cam follower is in an intermediate position along the loop. However, when the pushbutton is pulled from the panel to remove it from the switch assembly, the cam follower is moved from the initial position to an end position. When the pushbutton is replaced by pushing it back into position, the cam follower is moved along a return path portion of the loop against a stop position so that movement of the pushbutton is limited and the pushbutton can be reseated in the switch assembly without actuating the switch.
U.S. Pat. No. 4,096,368, which issued to Grebner on Jun. 20, 1978, describes a pushbutton switch which comprises a plurality of notched contact pins carried by respective legs of a linearly reciprocal pushbutton actuator for wiping bridging engagement with respective pairs of spaced stationary leaf spring contacts. The actuator is received in one end of a housing for longitudinal movement therein and the legs extend longitudinally into the housing. The spring contacts are mounted by circuit modules at the other end of the housing and extend longitudinally into the housing.
U.S. Pat. No. 3,947,651, which issued to Fuller on Mar. 30, 1976, discloses an electrical cartridge for interchangeable circuitry with a cap of a switch. The cartridge is interchangeably structured to accommodate various servo mechanisms for the switch or other operating unit within the cartridge. In addition, it is shaped to accommodate various electrical arrangements for the pushbutton cap which is slidably guided in the open end of the cartridge to operate the servo mechanism.
U.S. Pat. No. 3,602,678, which issued to Laete on Aug. 31, 1971, describes an illuminated pushbutton switch having a safety set and reset mechanism. A casing of the switch is provided with an aperture for receiving a pushbutton which comprises relatively moveable lamp holders and a pushing member with the pushbutton construction carrying a leaf spring that prevents the pushbutton construction from actuating the electrical switch structure of the casing when the pushbutton is initially inserted into the aperture until a releasing action of the pushbutton is accomplished.
U.S. Pat. No. 3,523,168, which issued to Holmes on Aug. 4, 1970, describes an illuminated pushbutton which has a tubular casing that receives a pushbutton structure at the upper end. It also has a lower switch structure at the lower casing end. The pushbutton can be placed in an operable locked condition to operate the switch as often as desired. The pushbutton can be removed from the casing by an upward or outward movement followed by an inward downward pushing action of the pushbutton means. After this movement, the pushbutton can be removed from the casing by an upward and outward movement action to remove the pushbutton from the casing.
U.S. Pat. No. 4,301,344, which issued to Sakakino et al on Nov. 17, 1981, discloses an illuminated pushbutton switch that comprises a housing, a switching component, a reset spring and an illuminator component including a lamp holder and a pushbutton which is removably installed in the housing. The switch also comprises a leaf spring which is secured at its base end to the lamp holder and disposed to provide a predetermined spacing between the lamp holder and the pushbutton.
Several of the patents described above provide a means which permits relamping of the switch and the subsequent resetting of the pushbutton in the housing without actuating the switch. However, the known techniques for accomplishing this relamping function can place a significant stress on relatively small and weak components. It would therefore be advantageous if a pushbutton switch is provided that permits relamping and subsequent resetting of the button within the housing without actuating the switch and which also utilizes a portion of the switch base in cooperation with a substantial part of the moving assembly to inhibit actuation of the switch during resetting of the button after relamping.